Influence of H2S on the thermal cracking of alkylbenzenes at high pressure (70 MPa) and moderate temperature (583–623 K)

• Published in: Journal of analytical and applied pyrolysis Vol. 140; pp. 423 - 433
• Main Authors: Burklé-Vitzthum, V., Leguizamon Guerra, N.C., Lorgeoux, C., Faure-Catteloin, D., Bounaceur, R., Michels, R.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-06-2019
• Subjects: Alkylbenzene; Apparent kinetic parameters; H2S; High pressure; Kinetic effect; Organosulfur compounds; Pyrolysis; Apparent kinetic parameters; Pyrolysis; H2S; Alkylbenzene; Kinetic effect; Organosulfur compounds; High pressure
• ISSN: 0165-2370; 1873-250X
• DOI: 10.1016/j.jaap.2019.04.025

[Display omitted]
•Pyrolysis of n-butylbenzene/H2S mixture (80%: 20% mol) at 70 MPa and from 583 K to 623 K was performed in sealed gold tubes.•The main products are toluene, ethylbenzene, iso-butylbenzene and hydrocarbon gases (C1, C2 and C3).•Several organosulfur compounds are produced: mainly short thiols, phenylbutanethiols, and phenylthiophenes.•H2S accelerates the pyrolysis of n-butylbenzene by a factor up to almost 4 depending on the experimental conditions.•The molecular composition of the products is highly modified in the presence of H2S.
The thermal cracking of n-butylbenzene was experimentally studied in the presence of H2S (80% : 20% mol) at high pressure (70 MPa), moderate temperature (583, 603 and 623 K) and for durations of 3, 7 and 15 days. The pyrolysis was performed in sealed gold tubes under isobaric conditions. Under these conditions, the conversion of n-butylbenzene varied between 2.5% and 73.2%. The pyrolysis of n-butylbenzene is accelerated by H2S by a factor of up to 3.6 depending on the operating conditions. This acceleration factor seems to decrease with increasing time and temperature. The apparent activation energy of the pyrolysis of n-butylbenzene decreases from 66.6 kcal/mol (pure n-butylbenzene) to 55.9 kcal/mol (n-butylbenzene in mixture with H2S). The main hydrocarbons produced are alkylbenzenes (mostly toluene and ethylbenzene), branched alkylbenzenes (mostly isomers of iso-butylbenzene and iso-heptylbenzene to a smaller extent) and short alkanes (from CH4 to C3). Several sulfur compounds are also produced and their relative abundances are in the range 4–16% depending on the operating conditions. These sulfur compounds are mostly short thiols (methanethiol, ethanethiol and propanethiols), phenylbutanethiols and phenylthiophenes. Additional experiments were also conducted with alkylbenzenes bearing shorter substituents than n-butylbenzene (toluene, ethylbenzene and n-propylbenzene) in order to hightlight the influence of the length of the side chain. Finally, the kinetic effect of H2S on the pyrolysis of n-butylbenzene was compared to its effect on n-octane pyrolysis: the effect seems antagonistic under the studied experimental conditions but some similarities can be highlighted.